The present invention relates to a method and apparatus for the introduction of a percutaneous flexible member and, more particularly, to a method and apparatus for the introduction of a flexible neural stimulator lead in the epidural space in the spinal cord of a patient.
In the past, neural stimulator leads have been implanted in the epidural space of the spinal cord of a patient for stimulating a selected location or locations along the spinal cord for such purposes as the relief of pain. Such leads have been introduced and fixed by the use of an epidural needle assembly such as, for example, a Tuohy needle. Tuohy needles typically include an elongate cannula into which an obturator is inserted. In practice, the needle cannula, with the obturator therein, is percutaneously inserted between vertebrae in the patient's spine so that the leading tip of the needle is in the patient's epidural space. Once this has been accomplished, the obturator is removed from the needle cannula and the neural stimulator lead is inserted through the cannula of the needle and into the epidural space where it is positioned and fixed at the location which is to be stimulated. Once positioning has been accomplished, the needle is withdrawn from the patient along the portion of the lead which extends from the patient's body and over the end of the lead. At this point, a terminal is formed upon or attached to the end of the lead and the terminal is electrically connected to a preferably subcutaneously implanted stimulator which generates electrical pulses or signals, as is known in the art, for the desired stimulation of the patient's spinal cord.
One difficulty which is presented in such prior method and apparatus is the fixing of the terminal to the end of the lead. It is preferable to mold or otherwise form the terminal on the end of the lead at the time of manufacture of the lead, rather than after the lead has been installed and fixed in the patient. Fixing of the terminal on the lead after fixation prolongs the procedure increasing the possibility of trauma to the patient, jeopardizes the maintenance of sterile conditions and precludes molding of the terminal directly to the lead.
The aforementioned installation and fixation procedure in which the needle cannula is ultimately withdrawn along the lead and over the end of the lead following installation and fixation precludes the mounting of a terminal at the time of manufacture which is larger in diameter than the diameter of the lead itself. This is because the diameter of the needle cannula is preferably only large enough to allow movement of the needle along the lead to withdraw the needle following lead installation. If such terminal is preattached to the lead at the time of manufacture, removal of the epidural needle assembly will be blocked. Thus, the prior methods and apparatus necessitated that the terminal at the end of the neural stimulator lead either be limited in diameter to the diameter of the lead, if the terminal was to be preattached to the lead at the time of manufacture, or required attachment following fixation of the lead. The former substantially limits the types of terminals which could be used and the latter prolongs the procedure, jeopardizes the maintenance of sterile conditions, increases the possibility of malfunction, and precludes molding of the terminal to the lead under manufacturing controlled conditions.
A method and apparatus incorporating the principles of the present invention, obviates the need for the removal of any component over the end of a neural stimulator lead after placement of the lead in the epidural space of the patient. The method and apparatus incorporating the principles of the present invention includes an introducer which is of inexpensive construction and is readily capable of manufacture, through which the lead is introduced and fixed in the epidural space of the patient. Once the lead has been introduced and fixed, the introducer may be easily withdrawn along the lead and split away from the lead before it reaches the end of the lead and the terminal. The ability to easily and quickly split the introducer away from the neural stimulator lead in the method and apparatus of the present invention enables the lead terminal, which may take a wide variety of forms, to be mounted to the lead at the time of manufacture and under assured sterile conditions, and reduces the time involved in the lead implantation procedure. Moreover, the introducer of the present invention need not be any larger in diameter than the prior needles which were previously employed in the installation of neural stimulator leads.
In one principal aspect of the present invention, a method of introducing a flexible member in the epidural space in the spinal cord of a patient comprises percutaneously inserting an introducer having an epidural needle assembly extending through a cannula in the introducer between vertebrae in the patient's spine so that the leading tip of the epidural needle assembly and the introducer are adjacent the epidural space of the patient. The epidural needle assembly is withdrawn from the cannula of the introducer and the flexible member which is to be introduced to the epidural space is inserted through the cannula of the introducer until the flexible member is positioned in the epidural space. The introducer is then withdrawn from the patient leaving the flexible member in the epidural space.
In still another principal aspect of the present invention, the aforementioned epidural needle assembly comprises a needle having a cannula and an obturator. The obturator is positioned in the cannula when the introducer and epidural needle assembly are being inserted between the vertebrae and the obturator is thereafter withdrawn from the cannula of the needle.
In still another principal aspect of the present invention, the aforementioned methods include withdrawal of the introducer from the patient along the flexible member and, once it is withdrawn from the patient, the cannula of the introducer is split away from the flexible member.
In still another principal aspect of the present invention, in the aforementioned methods, the flexible member is a neural stimulator lead.
In still another principal aspect of the present invention, apparatus for the introduction of a flexible member into the epidural space in the spinal cord of a patient includes an introducer having an elongate cannula and an epidural needle assembly removably insertable in and through the cannula. The tip of the epidural needle assembly extends beyond an end of the elongate cannula, whereby the introducer and epidural needle assembly may be percutaneously inserted together between vertebrae in the patient's spine so that the tip of the epidural needle assembly and the end of the elongate cannula are adjacent the epidural space of the patient when the epidural needle assembly is fully inserted into the cannula of the introducer. A flexible member is also provided which is inserted in and through the cannula and into the epidural space when the epidural needle assembly has been removed from the cannula of the introducer.
In still another principal aspect of the present invention, the last mentioned epidural needle assembly comprises a needle having a cannula and an obturator removably inserted in the cannula of the needle.
In still another principal aspect of the present invention, the introducer in the aforementioned apparatus includes means for splitting the introducer away from the flexible member after the flexible member has been inserted in and through the cannula of the introducer.
In still another principal aspect of the present invention, the flexible member in the aforementioned apparatus is a neural stimulator lead.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.